Protective relay system



R. M. SMITH PROTECTIVE RELAY SYSTEM Filed March 18, 1932 July 10, 1934.

iNvENToR Roy M. Smz'/I Bu AT NEY WITNESSES:

UNITED STATES PATENT OFFICE PROTECTIVE RELAY SYSTEM Roy M. Smith, NorthArlington, N. J., assigner to Westinghouse Electric 8.av Manufacturing.Company, a corporation of Pennsylvania Application March 18, 1932,Serial No. 599,697

8 Claims. (Cl. V75-294) My invention relates to relays and has par- Amoving contact 14 is secured to the spindle ticular relation to relaysin which a potential 13 and is arranged to bridge a pair of stationarycoil is employed. While not limited thereto, my contact members 15 whenthe disc is rotated in invention is particularly applicable toprotective one direction. A stop 17 is mounted in a posil relays for usein operating circuit breakers in tion to be engaged by the arm 14 tolimit the 60 response to predetermined electrical conditions rotation ofthe disc and spindle in the opposite occurring in an alternating-currentsystem. direction. n Y

It is an object of my invention to provide a Amagnetic vane armature ispivoted, at one relaywhich is responsive to predetermined voltend, to abracket 6 secured to one side of the age and current conditions, or topredetermined core 1. 'I'he free end of the armature 5 is posi- 65 powerconditions, in an alternating-current cirtioned to engage a contactmember '7,secured to cuit and in which the sensitiveness of the relaythe core 1, or a Contact member 8, ailixed to a is automaticallyincreased when the voltage of bracket 9. The bracket 9 is secured to thecore such circuit falls below a predetermined value. l, in any suitablemanner, by means of a screw 16 Another object of my invention is toprovide a l0 or other securing means. A coil spring 11 is 70. relay inwhich the entire potential coil is efecprovided for biasing the armature5 to the positively energized during `normal voltage conditions tion inwhich it engages the contact member l8. in an alternating-currentcircuit but in which 1 Under normal conditions, when the potential apart only of the potential coil is rendered eifeccoil 4 is fullyenergized, the armature 5 is held tive when the voltage of the circuitfalls below a in engagement with the contact member 'I against 75predetermined value. the bias of the spring 11, by the magnetic fluxAnother object of the present invention is to in the main pole of coremember 1. When the provide a protective relay of the induction typevoltage applied to the potential coil 4 falls below having meansincorporated therein for renderaA predetermined value, the decreasedmagnetic ,25 ing the relay inversely sensitive to the energizauxproduced by the coil in the main pole is in- 80 tion thereof. ysuflicient to maintainrthe armature 5 in engage- Other. objects of myinvention will become eviment with the contact member 7. The spring' 11dent from the following detailed description then causes the armature 5to rotate about its taken in conjunction with the accompanying pivotinto engagement with the contact member 8.

3.0 drawing, in which The contact member 7 is connected to one ter- 85Figure 1 is a schematic illustration in front minal of the potentialcoil 4, by means of a conelevation of a protective relay embodying myductor 18, so that voltage is applied to the entire invention. potentialcoil when the armature 5 is in engage- Fig. 2 is a side view of therelay shown in ment with. this contact member. The contact I Sii Fig. 1,and member 8 is connected to an intermediate tap 90 Fig. 3 is adiagrammatic view of a protective on the potential coil 4, by means of aconductor system utilizing my invention. 19. With such arrangement, onlya portion of Referring toFigs. l and 2 of the drawing, an the potentialcoil has voltage applied thereto when induction-disc type relay isillustrated as comthe armature is in engagement with the termi- `r40prising a magnetic core 1 having two depending nal 8. n 95 pole portionsupon which are mounted current The magnitude and direction of torqueacting coils 2 and 3, and having a third or main pole on the disc 12depends upon the magnitude and portion uponv which is mounted a voltagecoil 4. direction of power flowing in the alternating cur- Anon-magnetic disc 12, secured to a rotatable rent circuit to which therelay is adapted to be .'45 shaft or spindle 13, is positioned forrotation in connected. A decrease of voltage of the circuit 100 the airgap between the cores of the current and necessitates a correspondinglyhigher value of potentialcoils 2, 3 andr 4, respectively, in a usualcurrent in the circuit to operate the relay. Howmanner. The currentcoils 2 and 3 are conever,'if the voltage decreases below thepredeternected in series and, when energized, cooperate mined value atwhich the armature 5 is designed with the energized voltage coil 4 toproduce a to release, the armature disengages the contact 105 rotatingtorque acting on the disc armature 12. member '7 and moves intoengagement with the The magnitude yand direction of the torque iscontact member 8, thereby establishing a voltage determined by thevresultant fluxes produced by connection through part only of the turnsof pothe energized coils 2, 3 and 4 `acting on the disc tential coil 4.Because of the greatly reduced imf `5,5 armature 12. e pedance of thecircuit including the potential coil 4, the uX produced by the lattercoil increases, thereby reducing the value of current necessary tooperate the relay.

Referring more particularly to Fig. 3, I have illustrated oneapplication of my invention for the protection of a power circuit.Conductors L1 and L2 represent a suitable power circuit to which areconnected the primary windings of a current transformer 20 and apotential transformer 21. The current coils 2 and 3 of the relay areconnected to the secondary winding of the current transformer 2O bymeans of conductors 22 and 23 and the potential coil 4 is connected tothe secondary winding of the potential transformer 21, by means ofconductors 24 and 25. The conductor 24, however, is connected to thearmature 5 and is adapted to engage the contact members 7 or 8,depending on the voltage applied to the potential coil 4.

The stationary contact members 15 are connected in a circuit whichincludes a suitable source of energy, Such as a battery 26, and a tripcoil 27 of a circuit breaker 31 for opening the power circuit. Forsimplicity I have illustrated a circuit breaker of the manually reclosedtype; however it will be understood that my invention may be practicedwith any usual type of manually or automatically reclosed breaker and,of course, may be practiced in more elaborate protective systems thanthe one illustrated.

The operation of the scheme shown in Fig. 3 is as follows: Assuming thecircuit breaker to be closed and that power is flowing in the properdirection through conductors L1 and L2, a current proportional to themain current flows through the current coils 2 and 3, and a voltagepropontional to the main voltage is impressed upon the entire potentialcoil 4. The magnetic ux pro duced by the potential coil 4 maintains thearmature 5 in engagement with the contact member 7 as long as thevoltage between the main conductors L1 and L2 remains normal. Therotating eld produced jointly by the current and potential coils rotatesthe disc 12 and spindle 13 in the usual manner until the moving contact14 strikes the stop 17. The relay then remains in this position as longas normal conditions exist in the power circuit.

Assuming, however, that some abnormal condition occurs in the powercircuit which causes the voltage applied to the potential coil 4, tofall below the predetermined value at which the armature 5 is designedto operate, then the magnetic ux produced by the potential coildecreases, so that the spring 11 causes the armature 5 to rotate aboutits pivot into engagement with the contact member 8.

This reduces the impedance of the circuit including the potential coil4, in the manner pref kviously described, and causes the ux produced bythe latter coil to increase. If now the direction of power ow in themain conductors L1 and L2 reverses, the direction of torque applied tothe disc 12 reverses, and the moving contact 14 moves into engagementwith the contact members 15. Because of the increased flux produced bycoil 4, a minimum of reverse current is required for the performance orthe latter operation. Upon the engagement of the moving contact 14 withthe stationary contacts 15, a circuit is completed for the trip coil 27of the circuit breaker. The circuit breaker 31 is thereupon actuated toits open position and the circuit breaker may be manually reclosed inthe' usual manner when the fault or abnormal power con# dition onconductors L1 and L2 is remedied.

It is, therefore, apparent to those skilled inthe art that I haveprovided a relay that is sensitive to predetermined voltage and current,or to predetermined pow er conditions, and in which the sensitiveness ofthe relay is automatically in"-r creased whenl the voltage of the powersystem falls below a predetermined denite value. The relay is,furthermore, sensitively responsive to reversal of power with moderateValues of reverse current in the power circuit under a wide range ofvalues of line voltage.

Although I have shown one specic embodiment of my invention I do notdesire to be limited thereto as various other modications may be madewithout departing from the spirit and scope of the appended claims.

I claim as my invention:

l. In protective apparatus for an electric circuit, a circuit breakerfor controlling said circuit, control means for said circuit breakerincluding a relay having coil means, energizing means for said relayincluding electrical connections for normally energizing a predeterminednumber of turns of said coil means in accordance with an electricalcondition of said circuit, and means responsive to a predeterminedreduction of voltage in said circuit for modifying said connections tocause a different predetermined number of turns of saidcoil means to beenergized in accordance with said electrical condition, to thereby alterthe sensitiveness of said relay under low voltage conditions of saidcircuit.

2. In protective apparatus for an electric circuit, a circuit breakerfor controlling said circuit, control moans for said circuit breakerincluding a relay having a'magnetic core, a coil in inductiverelationshipA to said core and a main armature responsive to a magneticcondition of said core, energizing means for said relay includingelectrical connections between said circuit and said coil for normallymaintaining a predetermined ratio between an electrical condition ofsaid circuit and a-magnetomotive force applied to said core, and meansincluding an auxiliary armature responsive to a predetermined abnormalflux condition of said core for modifying said connections to establishadifferent predetermined ratio between said electrical condition of saidcircuit and said magnetomotive force.

3. In a protective system, an electrical circuit, a circuit breaker forinterrupting said circuit, means for actuating said circuit breaker uponthe occurrence of predetermined electrical conditions in said circuitincluding a relay having a potential coil and a potential circuit forapplying a voltage to said coil, and means associated with said coilresponsive to a predetermined decrease of voltage of said circuit forexcluding the entire potential coil from said potential circuit andinserting a portion only of said coil insad potential circuit toincrease the sensirzveness o1' said relay.`

4. In a relay, a magnetic structure having a plurality of spaced polemembers defining an air gap, a plurality of coils mounted upon said polemembers, a disc armature pivotally mounted for rotation in said air gap,contact members controlled by said disc armature, energizing connectionsfor said coils including a circuit of predetermined impedance phaseangle for energizing one of said coils, an auxiliary armature mounted tomove in response to variations of flux in one cf said pole members,auxiliary contact members controlled by irs said auxiliary armature, andmeans including said auxiliary contact members for altering theelectiveness of said one of said coils while maintaining said imped'ancephase angle substantially unchanged.

5. In protective apparatus for an alternating current circuit, a circuitbreaker for controlling said circuit, control means for said circuitbreaker including a relay having a magnetic core, a firstr coil ininductive relationship to said core, a second coil and an elementresponsive to a vector product of magnetic conditions produced by saidcoils, energizing means for said relay including electrical connectionsfor normally maintaining a predetermined ratio and a predetermined phaserelationship between an electrical condition of said circuit and amagnetic condition produced by said first coil, and means responsive toa predetermined abnormal ilux condition of said core for modifying saidconnections to establish a different predetermined ratio and to maintainsubstantially the same predetermined phase relationship between saidelectrical condition and said magnetic condition, to thereby alter thesensitiveness but not the phase angle characteristics of said relayduring an abnormal condition of said circuit.

6. In a relay, a magnetic structure having a plurality of spaced polemembers defining an air gap, current coils and a potential coll mountedupon said pole members, a disc armature pivotally mounted for rotationin said air gap, contact members controlled by said disc armature, anauxiliary armature mounted to move in response to variations of voltageimpressed upon said potential coil, and means including contact memberscontrolled by said auxiliary armature for causing a predeterminedvoltage to be impressed upon the entire potential coil or a portion onlyof said coil depending upon the variation of the impressed voltage.

7. In a relay, a magnetic structure having a. plurality of spaced polemembers defining' an gap, current coils and a potential coil mountedupon said pole members for operating said relay when current and voltageare applied to the respective coils, a disc armature pivotally' mountedforr rotation in said air gap', contact members controlled by said discarmature, anv auxiliary armature mounted to move in response tovariations off flux produced by said potential coil, and means includingcontact members controlled by said auxiliary armature for causing saidvoltagel to be impressed upon the entire potential coil when saidvvoltage is above a predetermined value, or to be applied to a portiononly of said coil when said voltage is below a predetermined value, tothereby reduce the value of current necessary to operate said relayduring an undervoltage condition.

8. In a. protective system, an electrical circuit, a circuit breaker forinterrupting said circuit, means for actuating said circuit breaker uponthe occurrence of a predetermined electrical condition in said circuitincluding a relay comprising a magnetic structure having a plurality ofspaced pole members defining an air gap, current coils and a potentialcoil mounted upon said pole members, a disc armature pivotally mountedfor rotation in said air gap, contact members controlled by said discarmature, a magnetic armature mounted to move in response to variationsof voltage impressed upon said potential coil, and means includingcontact members controlled by said magnetic armature for causing apredetermined voltage to be impressed upon the entire potential coil ora portion only of said coil to increase the sensitiveness of said relay.

ROY M. SMITH.

